Method and apparatus of initial access in next generation cellular networks

ABSTRACT

A communication method and system for converging a fifth generation (5G) communication system for supporting higher data rates beyond a fourth generation (4G) system with a technology for internet of things (IoT) are provided. The communication method and system may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method of a terminal for receiving data in a cellular network is provided. The method comprises receiving a synchronization signal block (SS block) including at least one synchronization signal and a broadcast channel from a base station, identifying an offset between the SS block and a resource block (RB) grid from system information in the broadcast channel, and determining the resource block grid based on the offset.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/607,881, filed on Oct. 24, 2019, which application is a U.S.National Stage application under 35 U.S.C. § 371 of an Internationalapplication number PCT/KR2018/005109, filed on May 2, 2018, which isbased on and claims priority under 35 U.S.C. § 119(e) of a U.S.Provisional application Ser. No. 62/500,401, filed on May 2, 2017, inthe U.S. Patent and Trademark Office, of a U.S. Provisional applicationSer. No. 62/520,404, filed on Jun. 15, 2017, in the U.S. Patent andTrademark Office, and of a U.S. Provisional application Ser. No.62/556,142, filed on Sep. 8, 2017, in the U.S. Patent and TrademarkOffice, the disclosure of each of which is incorporated by referenceherein in its entirety.

TECHNICAL FIELD

The disclosure relates to a method and an apparatus forreceiving/transmitting data in a cellular network. More particularly,the disclosure relates an initial access in next generation cellularnetworks.

BACKGROUND ART

To meet the demand for wireless data traffic having increased sincedeployment of fourth generation (4G) communication systems, efforts havebeen made to develop an improved fifth generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘beyond 4G network’ or a ‘post long term evolution(LTE) System’. The 5G wireless communication system is considered to beimplemented not only in lower frequency bands but also in higherfrequency (mmWave) bands, e.g., 10 GHz to 100 GHz bands, so as toaccomplish higher data rates. To mitigate propagation loss of the radiowaves and increase the transmission distance, the beamforming, massivemultiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, and large scale antennatechniques are being considered in the design of the 5G wirelesscommunication system. In addition, in 5G communication systems,development for system network improvement is under way based onadvanced small cells, cloud radio access networks (RANs), ultra-densenetworks, device-to-device (D2D) communication, wireless backhaul,moving network, cooperative communication, coordinated multi-points(CoMP), reception-end interference cancellation and the like. In the 5Gsystem, hybrid frequency shift keying (FSK) and quadrature amplitudemodulation (QAM) (FQAM) and sliding window superposition coding (SWSC)as an advanced coding modulation (ACM), filter bank multi carrier(FBMC), non-orthogonal multiple access (NOMA), and sparse code multipleaccess (SCMA) as an advanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies, suchas a sensor network, MTC, and M2M communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RAN as theabove-described big data processing technology may also be considered tobe as an example of convergence between the 5G technology and the IoTtechnology.

In the recent years several broadband wireless technologies have beendeveloped to meet the growing number of broadband subscribers and toprovide more and better applications and services. The second generation(2G) wireless communication system has been developed to provide voiceservices while ensuring the mobility of users. The third generation (3G)wireless communication system supports not only the voice service butalso data service. The 4G wireless communication system has beendeveloped to provide high-speed data service. However, the 4G wirelesscommunication system suffers from lack of resources to meet the growingdemand for high speed data services. Therefore, the 5G wirelesscommunication system is being developed to meet the growing demand ofvarious services with diverse requirements, e.g., high speed dataservices, ultra-reliability, low latency applications and massivemachine type communication. Due to the widely supported services andvarious performance requirements, there is high potential that the userequipment (UE) may have different capabilities, e.g., in terms ofsupported UE bandwidth (BW). Flexible UE bandwidth support needs to beconsidered in the design of 5G network, and the flexible network accessfor UEs with different bandwidth capabilities.

In the 4G LTE networks, flexible system bandwidth is supported (e.g.,1.4 MHz/3 MHz/5 MHz/10 MHz/15 MHz/20 MHz), and the channel designs aremostly based on the operated system bandwidth. This gives mandatoryrequirement that the UE should operate in the same bandwidth with thesystem, except in initial access when UE has no information of thesystem bandwidth. Since the UEs have no information of the systembandwidth in the initial access, the essential signals and channels aretransmitted based on a pre-defined bandwidth, e.g., the minimumbandwidth supported by the networks.

FIG. 1 illustrates system operation in LTE.

As shown in FIG. 1, the transmission of the synchronization signals(e.g., primary synchronization signal (PSS) and secondarysynchronization signal (SSS)) and broadcast channel (e.g., physicalbroadcast channel (PBCH)) is fixed in the center of the system bandwidthand limited within a pre-defined bandwidth, which is accessible to allUEs. After receiving the PBCH, it is possible that the UEs obtain thesystem bandwidth, which is indicated in the master information block(MIB) carried by PBCH. The transmissions of other channels/signalsoccupy the full system bandwidth, because the UEs can access the actualsystem bandwidth after obtaining the system bandwidth information.

FIG. 2 shows a flowchart of UE performing initial access.

Referring to FIG. 2, UE searches PSS/SSS at operation 210. If UE detectsPSS/SSS, UE derives a center frequency of the system bandwidth andobtains symbol/slot/frame boundary based on the PSS/SSS at operation220. Based on the information derived and obtained at operation 220, UEreceives PBCH and decode MIB at operation 230. UE obtains information onsystem frame number (SFN), system bandwidth, etc. from the decoded MIBat operation 240. UE searches PDCCH in full system bandwidth to receivesystem information at operation 250.

Meanwhile, for the UEs with less bandwidth than the system bandwidth, itis impossible for the UEs to access the channel which occupies fullsystem bandwidth. There is limitation of the current systems to supportflexible access for UEs with various bandwidths.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

DISCLOSURE OF INVENTION Technical Problem

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea communication method and system for converging a fifth generation (5G)communication system for supporting higher data rates beyond a fourthgeneration (4G) system.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

The disclosure provides a method and an apparatus forreceiving/transmitting data in a cellular network.

The disclosure provides a method and an apparatus for an initial accessin next generation cellular networks.

The disclosure provides a method and an apparatus for supportingflexible access for terminals with various bandwidths.

Solution to Problem

In accordance with a first aspect of the disclosure, a method of aterminal for receiving data in a cellular network is provided. Themethod includes receiving a synchronization signal block (SS block)including at least one synchronization signal and a broadcast channelfrom a base station, identifying an offset between the SS block and aresource block (RB) grid from system information in the broadcastchannel, and determining the RB grid based on the offset.

In accordance with a second aspect of the disclosure, a method of a basestation for transmitting data in a cellular network is provided. Themethod includes determining a resource block (RB) grid and a location ofa synchronization signal block (SS block) including at least onesynchronization signal and a broadcast channel and transmitting the SSblock based on the RB grid to a terminal. An offset between the SS blockand the RB grid is transmitted in system information through thebroadcast channel.

In accordance with a third aspect of the disclosure, a terminal forreceiving data in a cellular network is provided. The terminal includesa transceiver and a controller coupled with the transceiver. Thetransceiver is configured to receive signals from a base station and totransmit signals to the base station. The controller is configured tocontrol the transceiver to receive a synchronization signal block (SSblock) including at least one synchronization signal and a broadcastchannel from the base station, identify an offset between the SS blockand a resource block (RB) grid from system information in the broadcastchannel, and determine the RB grid based on the offset.

In accordance with a fourth aspect of the disclosure, a base station fortransmitting data in a cellular network is provided. The base stationincludes a transceiver and a controller coupled with the transceiver isprovided. The transceiver is configured to receive signals from aterminal and to transmit signals to the terminal. The controller isconfigured to determine a resource block (RB) grid and a location of asynchronization signal block (SS block) including at least onesynchronization signal and a broadcast channel, control the transceiverto transmit the SS block based on the RB grid to the terminal, andcontrol the transceiver to transmit an offset between the SS block andthe RB grid in system information through the broadcast channel to theterminal.

Advantageous Effects of Invention

Flexible access for terminals may be supported with various bandwidths.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates system operation in Long Term Evolution (LTE);

FIG. 2 shows a flowchart of user equipment (UE) performing initialaccess;

FIG. 3 shows an example of resource grid structure of an orthogonalfrequency division multiplexing (OFDM) based communication system;

FIG. 4 shows an example of same size of channel raster andsynchronization raster;

FIG. 5 shows another example of same size of channel raster andsynchronization raster;

FIG. 6 shows an example of different size of channel raster andsynchronization raster;

FIG. 7 shows an example of SS Block including primary synchronizationsignal (PSS), secondary synchronization signal (SSS)) and physicalbroadcast channel (PBCH);

FIG. 8 shows an example of valid candidate for synchronization signalblock (SS block) center frequency;

FIG. 9 shows another example of valid candidate center frequency for theSS block;

FIG. 10 shows an example of valid candidate for SS block centerfrequency;

FIG. 11 shows another example of subset of valid candidate centerfrequency for the SS block;

FIG. 12 shows an example of different size of channel raster andsynchronization raster;

FIG. 13 shows an example of candidate center frequency for SS block withdifferent size of channel raster and synchronization raster;

FIG. 14A shows an example of a valid SS block candidate center frequencyfor both a narrowband carrier and a wideband carrier;

FIG. 14B shows another example of valid SS block candidate centerfrequency for both narrowband carrier and wideband carrier;

FIG. 15 shows an example of arbitrary subcarrier level offset between SSblock RB grid and actual system RB grid;

FIG. 16 shows an example of misalignment between SS block resource block(RB) grid and actual system RB grid;

FIG. 17 is a flowchart of gNB procedure to determine SS block centerfrequency and make indication to UE;

FIG. 18 is a flowchart of UE procedure to search SS block centerfrequency and derive carrier center frequency;

FIG. 19 shows an example of carrier center frequency indication inmaster information block (MIB);

FIG. 20 shows an example of carrier center frequency indication inremaining minimum system information (RMSI);

FIG. 21 shows an example of bandwidth (BW) dependent indication of SSblock location in MIB;

FIGS. 22A and 22B are a flowchart of gNB procedure to determine SS blockcenter frequency and make indication to UE;

FIG. 23 is a flowchart of UE procedure to search SS block centerfrequency and derive carrier center frequency;

FIG. 24 shows an example of a network configuring a carrier index to theUE;

FIG. 25 is a flowchart of UE to obtain information of multiple carriersand carrier assigned to the UE;

FIGS. 26, 27 and 28 illustrate multiple SS blocks in a single carrier;

FIG. 29 is a flowchart of UE to obtain information of multiple SSblocks;

FIG. 30 illustrates multiple SS blocks transmitted in a widebandcarrier;

FIGS. 31A, 31B and 31C are examples of indication of RMSI controlresource set (CORESET) frequency location;

FIG. 32 shows UE procedure to obtain RMSI CORESET frequency resourcelocation information;

FIG. 33 shows an example of indication of limited cases of RMSI CORESETfrequency location;

FIG. 34 shows another example of indication of RMSI CORESET frequencylocation;

FIGS. 35, 36 and 37 show examples of indication cases of RMSI CORESETfrequency location;

FIG. 38 shows an example of RMSI CORESET location cases for the samesubcarrier spacing case;

FIG. 39 shows an example of RMSI CORESET location cases for thedifferent subcarrier spacing case;

FIG. 40 is a block diagram of a terminal according to an embodiment ofthe disclosure; and

FIG. 41 is a block diagram of a base station according to an embodimentof the disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

MODE FOR THE INVENTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

It is known to those skilled in the art that blocks of a flowchart (orsequence diagram) and a combination of flowcharts may be represented andexecuted by computer program instructions. These computer programinstructions may be loaded on a processor of a general purpose computer,special purpose computer, or programmable data processing equipment.When the loaded program instructions are executed by the processor, theycreate a means for carrying out functions described in the flowchart.Because the computer program instructions may be stored in a computerreadable memory that is usable in a specialized computer or aprogrammable data processing equipment, it is also possible to createarticles of manufacture that carry out functions described in theflowchart. Because the computer program instructions may be loaded on acomputer or a programmable data processing equipment, when executed asprocesses, they may carry out operations of functions described in theflowchart.

A block of a flowchart may correspond to a module, a segment, or a codecontaining one or more executable instructions implementing one or morelogical functions, or may correspond to a part thereof. In some cases,functions described by blocks may be executed in an order different fromthe listed order. For example, two blocks listed in sequence may beexecuted at the same time or executed in reverse order.

In this description, the words “unit”, “module” or the like may refer toa software component or hardware component, such as, for example, afield-programmable gate array (FPGA) or an application-specificintegrated circuit (ASIC) capable of carrying out a function or anoperation. However, a “unit”, or the like, is not limited to hardware orsoftware. A unit, or the like, may be configured so as to reside in anaddressable storage medium or to drive one or more processors. Units, orthe like, may refer to software components, object-oriented softwarecomponents, class components, task components, processes, functions,attributes, procedures, subroutines, program code segments, drivers,firmware, microcode, circuits, data, databases, data structures, tables,arrays or variables. A function provided by a component and unit may bea combination of smaller components and units, and may be combined withothers to compose larger components and units. Components and units maybe configured to drive a device or one or more processors in a securemultimedia card.

Prior to the detailed description, terms or definitions necessary tounderstand the disclosure are described. However, these terms should beconstrued in a non-limiting way.

The “base station (BS)” is an entity communicating with a user equipment(UE) and may be referred to as BS, base transceiver station (BTS), nodeB (NB), evolved NB (eNB), access point (AP), or 5G NB (5GNB).

The “UE” is an entity communicating with a BS and may be referred to asthe UE, device, mobile station (MS), mobile equipment (ME), or terminal.

A. Basic Operation

Considering an orthogonal frequency division multiplexing (OFDM) basedcommunication system, a resource element can be defined by a subcarrierduring on OFDM symbol duration. In the time domain, a transmission timeinterval (TTI) can be defined which is composed of multiple OFDMsymbols. In the frequency domain, a resource block (RB) can be definedwhich is composed of multiple OFDM subcarriers.

FIG. 3 shows an example of resource grid structure of an OFDM basedcommunication system.

As shown in FIG. 3, the resources can be divided into TTIs in timedomain and RBs in frequency domain. Typically, a RB can be a baselineresource unit for resource mapping and scheduling in the frequencydomain.

As described in FIG. 2, when a UE accesses to a network, UE firstsearches the synchronization signals, e.g., a primary synchronizationsignal (PSS) and a secondary synchronization signal (SSS), to obtaintime/frequency synchronization and cell identifier (ID). Similar asother cellular networks, the deployment of the next generation cellularsystem needs to consider the channel raster requirement. For example inLong Term Evolution (LTE), the channel raster is Δf_(ch_raster)=100 kHzfor all bands, which means that the carrier center frequency is aninteger multiple of 100 kHz. The candidates for a carrier centerfrequency can be expressed by f_(n)±f₀+n×Δf_(ch_raster), where f₀ is areference frequency in a certain frequency band, e.g., f₀=0 Hz and n isan integer number to derive a certain carrier center frequency f_(n).The carrier can be located around a certain center frequency candidatewith a given carrier bandwidth.

The size of the synchronization raster Δf_(sync_raster) determines thegranularity that UEs search the synchronization signals in a frequencyrange, e.g., the PSS/SSS in LTE.

FIG. 4 shows an example of same size of channel raster andsynchronization raster.

As shown in the example in FIG. 4, if the synchronization raster is thesame as the channel raster, e.g., Δf_(sync_raster)=Δf_(ch_raster)=100kHz, a candidate of carrier center frequency is also a candidate ofcenter frequency for the synchronization signals. In this case, whichmay be the case in LTE, the center frequency for the synchronizationsignals can be fixed to the center frequency for a carrier. Here thesynchronization signal block (SS block) may include PSS, SSS andphysical broadcast channel (PBCH). When a UE is turned on, UE searchesthe synchronization signals from the SS block center frequencycandidates with a step of synchronization raster Δf_(sync_raster). If aUE detects the synchronization signals in a certain frequency f_(n), theUE assumes that f_(n) is the SS block center frequency as well as thecenter frequency of the current carrier.

To allow flexible deployment, it is not mandatory that the SS blockcenter frequency is the same as the center frequency of thecorresponding carrier.

FIG. 5 shows another example of same size of channel raster andsynchronization raster.

As shown in the example of FIG. 5, the carrier center frequency isf_(n), and there are multiple SS block center frequency candidateswithin the carrier. The SS block can be located in a center frequencycandidate f_(m), which is different from f_(n). In this case, when a UEis turned on, UE searches the synchronization signals from the SS blockcenter frequency candidates. If a UE detects the synchronization signalsin a certain frequency f_(m), the UE cannot assume that the detectedfrequency f_(m) is the same as the center frequency of the currentcarrier.

The size of synchronization raster can be different per frequency range.For example, for frequency ranges supporting a wider carrier bandwidthand operation in a wider frequency spectrum (e.g. above 6 GHz), thelarger synchronization raster size can be used, to reduce the searchingtime for initial access.

FIG. 6 shows an example of different size of channel raster andsynchronization raster.

As shown in the example of FIG. 6, the size of synchronization raster islarger than the size of the channel raster, i.e.,Δf_(sync_raster)>Δf_(ch_raster). The candidates of carrier centerfrequency can be expressed by f_(ch,n)=f₀+n×Δf_(ch_raster), while thecandidates of SS block center frequency can be expressed byf_(sync,m)=f₀+m×Δf_(sync_raster). Assuming thatΔf_(sync_raster)=k×Δf_(ch_raster), where k is a pre-defined positiveinteger number to denote the ratio of synchronization raster size andchannel raster size, the candidates of SS block center frequency are ktimes sparser compared to the candidates of the carrier centerfrequency. Different value of k can be used in different frequencyranges. Similarly, it is not possible that the SS block center frequencyalways aligns with the center frequency of the corresponding carrier. Ifa UE detects the synchronization signals based on the synchronizationraster in a certain frequency f_(sync,m), the UE cannot assume that thedetected frequency f_(sync,m) is the same as the center frequency of thecurrent carrier.

Therefore, compared to the conventional cellular systems, there is aneed to inform UEs where the SS block center frequency is and where theactual carrier center frequency location is. Then based on the systembandwidth information, the actual frequency resources occupied by thecarrier in the frequency band can be obtained by UEs.

FIG. 7 shows an example of SS Block including PSS, SSS and PBCH.

Referring to FIG. 7 showing the example of SS block, it has two types ofsynchronization signals; PSS and SSS, and one broadcast channel, PBCH.PSS, SSS and PBCH can be transmitted within an SS block in a timedivision multiplexing (TDM) manner. New radio-PBCH (NR-PBCH) is anon-scheduled broadcast channel carrying at least a part of minimumsystem information (master information block, MIB) and periodicitypredefined depending on carrier frequency range. In the example of FIG.7, the PSS is transmitted in 144 subcarriers in one OFDM symbol, so doesSSS. The PBCH is transmitted in 288 subcarriers during two OFDM symbols.For a given frequency band, the SS blocks can be transmitted based on adefault subcarrier spacing in the pre-defined time and frequencyresources. UE may be able to identify OFDM symbol index, slot index in aradio frame and radio frame number from an SS block. Some otherremaining minimum system information, e.g., denoted by RMSI or systeminformation block 1 (SIB1), can be scheduled by a control channel andtransmitted in a data channel.

B. Determination of SS Block Center Frequency

Assume that a base station (denoted by gNB for next generation cellularnetworks) decides the carrier center frequency and carrier bandwidth ina frequency range, there may be multiple SS block center frequencycandidates which can be searched by UE based on the synchronizationraster size. Based on predefined rules or conditions, there can be oneor more valid SS block center frequency candidates which are valid fortransmission of a SS block in a given carrier. The rules or conditionsare predefined and are known to both gNB and UEs. The number of valid SSblock center frequency candidates can be determined by considering thecarrier bandwidth (BW), carrier center frequency, and channel rastersize and synchronization raster size. The gNB may select one valid SSblock center frequency candidate for transmission of a SS block in acarrier. To enable UE obtain the information of carrier center frequencyand/or other related information, gNB may need to send extra indicationif there are multiple valid SS block center frequency candidates.Different methods can be considered to determine the valid SS blockcenter frequency candidates.

Case with Same Size of Channel Raster and the Synchronization Raster

In case that the size of channel raster and the synchronization rasteris the same, i.e., Δf_(sync_raster)Δf_(ch_raster), the following methodsto determine valid SS block center frequency candidates can beconsidered.

Method 1: In a given carrier, there is one valid SS block centerfrequency candidate, which has a predefined relationship with the centerfrequency for a carrier. For example, the SS block center frequency canbe the same as the center frequency of a carrier. After the gNBdetermines the center frequency for a carrier, e.g., f_(n), the centerfrequency for the carrier is by default the center frequency fortransmission of the SS block. This is the case shown in FIG. 4 describedabove. In this case, there is no need of indication about the locationof SS block and carrier center frequency, since the location of SS blockand carrier center frequency can be derived by UE based on thepredefined relationship.

Method 2: In a given carrier, there are more than one valid SS blockcenter frequency candidates. There are some pre-defined restrictions onthe valid SS block center frequency candidates in the carrier.

Embodiment 1: One restriction of the valid SS block center frequencycandidates can be that at least the SS block transmission is not out ofthe carrier BW, which can be expressed by

${{{f_{n} - f_{m}}} \leq \frac{{BW_{carrier}} - {BW_{SS}}}{2}},$

where BW_(carrier) is the carrier BW, or can be considered the actualtransmission BW considering any possible guard band in the edge sides ofthe carrier, BW_(SS) is the BW of the SS block. f_(n) is the carriercenter frequency determined by the gNB, and f_(m) is the valid candidatefor SS block center frequency.

FIG. 8 shows an example of valid candidate for SS block centerfrequency.

In the example of FIG. 8, the several candidates for the SS block centerfrequency around the carrier center frequency are valid, but the severalcandidates for the SS block center frequency in both edge sides of thecarrier are not valid.

Embodiment 2: Additional restriction of the valid SS block centerfrequency candidates can be the additional alignment in the frequencyresource grid in the carrier. For example, the resource grid in thefrequency domain can be determined based on the carrier centerfrequency, subcarrier spacing, and RB size, and so on. Given a carriercenter frequency determined by gNB, the valid SS block center frequencycandidates can be restricted to the ones aligned with a certain resourcegrid, e.g., aligned with the RB boundary or RB center in the carrier.When aligned with RB boundary, the condition can be expressed bymod(|f_(n)−f_(m)|, BW_(RB))=0 where BW_(RB) is the RB size with thesubcarrier spacing used in the SS block, f_(n) is the carrier centerfrequency determined by the gNB, and f_(m) is the valid candidate of SSblock center frequency. This may make the resource mapping ofsynchronization signals easier, since the resource mapping is usuallybased on the unit of RBs.

FIG. 9 shows another example of valid candidate center frequency for theSS block.

For example, the same size of channel raster and synchronization rasteris used, e.g., 100 kHz, and the RB size is 180 kHz assuming subcarrierspacing of 15 kHz and 12 subcarriers per RB. Referring to FIG. 9, the RBboundary is aligned with carrier center frequency. The carrier centerfrequency is one valid candidate of SS block center frequency, and thenext valid candidate is 900 kHz farther from the carrier centerfrequency, to make the SS block center frequency aligned with RBboundary. In other words, the offset between two valid candidates of SSblock center frequency is the lowest common multiple of the size ofsynchronization raster and size of RB.

Embodiment 3: One restriction of the valid SS block center frequencycandidates can be that only a subset of SS block center frequencysatisfying a pre-defined rule.

FIG. 10 shows an example of valid candidate for SS block centerfrequency.

Referring to FIG. 10, the subset can be compromised by the L valid SSblock center frequency candidates, which are closest to the carriercenter frequency.

FIG. 11 shows another example of subset of valid candidate centerfrequency for the SS block.

Alternatively, referring to FIG. 11, the subset can be compromised bythe L valid candidate center frequency for the synchronization signals,where the two neighbor candidates has a pre-defined separation, e.g., apre-defined integer times of channel raster size, or RB size, etc.

The size of L can be pre-defined, or depend on the system bandwidth.

Embodiment 4: The combination of the above conditions, e.g., inEmbodiment 1 and 2 and other conditions and restrictions can also beconsidered. The pre-defined conditions are known to both gNB and UE.

In method 2, the number of valid SS block center frequency candidatesmay be determined by the carrier BW, channel raster size, and RB size,etc. Assuming that the channel raster is fixed at least in a givenfrequency band, and RB size is known to the UE based on detection of SSblock, the UE at least needs to know the BW information and hence toknow how many valid center frequency candidates for SS block. Then, theselected valid candidate can be indicated to the UE. The number of validcenter frequency candidates affects the indication overhead. If the BWinformation is not available, the SS block location in the carrier canbe indicated, which enable UE to derive partial carrier information,e.g., the lowest frequency edge side in the carrier.

Case with Different Size of Channel Raster and the SynchronizationRaster

The following describes the case that the synchronization raster size islarger than the channel raster size, i.e.,Δf_(sync_raster)>Δf_(ch_raster). It is assumed thatΔf_(sync_raster)=k×Δf_(ch_raster), where k is a pre-defined positiveinteger number. In other words, the center frequency candidates forsynchronization signals are k times sparser compared to the centerfrequency candidates for the carrier.

FIG. 12 shows an example of different size of channel raster andsynchronization raster.

Specifically, the example of k=3 is shown in FIG. 12. The candidates ofcarrier center frequency can be expressed byf_(ch,n)=f₀+n×Δf_(ch_raster), while the candidates of center frequencyfor the synchronization signals can be expressed byf_(sync,m)=f₀+m×f_(sync_raster). The following methods can be consideredto determine valid candidates of center frequency for thesynchronization signals.

Method 1: In a given carrier, there is one valid candidate of SS blockcenter frequency. After the gNB determines the center frequency for acarrier, e.g., f_(ch,n), the valid candidate of SS block centerfrequency f_(sync,m), can be determined by a pre-defined rule.

Embodiment 1: The first candidate of SS block center frequency in thehigher frequency side than the carrier center frequency is the validone, which can be expressed by f_(sync,m)≥f_(ch,n) &m=min_(m)(f_(sync,m)−f_(ch,n)). For example in FIG. 12, f_(sync,m+1) isthe valid candidate of center frequency for SS block transmission.

Embodiment 2: The first candidate of SS block center frequency in thelower frequency side than the carrier center frequency is the valid one,which can be expressed by f_(sync,m)≤f_(ch,n) &m=min_(m)(f_(ch,n)−f_(sync,m)). For example in FIG. 12, f_(sync,m) isthe valid candidate of center frequency selected for transmission of SSblock.

Embodiment 3: The closest candidate of SS block center frequency to thecarrier center frequency is the valid one, which can be expressed bym=min_(m)|f_(ch,n)−f_(sync,m)|. For example in FIG. 12, f_(sync,m) isthe valid candidate of center frequency selected for transmission of SSblock since f_(sync,m) is the closest candidate of SS block centerfrequency to the carrier center frequency. In case there can be multiplecandidates with same minimum distance to the carrier center frequency, apre-defined rule can be used to select one from them, e.g., thecandidate in the higher frequency side than the carrier center frequencyor in the lower frequency side.

In this method, even though there is one valid candidate of SS blockcenter frequency, indication is still needed to enable UE derive thecarrier center frequency, because the size of channel raster andsynchronization raster is different. For the embodiments above, UE needsto know the location difference between the carrier center frequency andSS block center frequency. There are k possibilities, which can beindicated by ┌log₂ k┐ bits to derive the relative location difference.

Additional conditions in the above embodiments can be also considered toselect the valid candidate of center frequency for transmission of SSblock. For example, the valid SS block center frequency candidate can berestricted to the ones aligned with the RB boundary or RB center in thecarrier. The condition can be expressed bymod(|f_(ch,n)−f_(sync,m)|,BW_(RB))=0 where BW_(RB) is the RB size withthe subcarrier spacing used in the SS block. This condition can beconsidered together in the above embodiments to determine the centerfrequency candidate for transmission of SS block.

FIG. 13 shows an example of candidate center frequency for SS block withdifferent size of channel raster and synchronization raster.

As shown in the example in FIG. 13, f_(sync,m) is the valid centerfrequency selected for transmission of SS block, considering theconditions of Embodiment 3 and RB boundary alignment. In this case, ifthe relative distance between the carrier center frequency and areference SS block center frequency candidate is indicated, the locationof carrier center frequency can be derived by UE in an implicit manner,by applying the RB boundary alignment condition. For example,considering that the reference SS block center frequency candidate isthe one in the lower or higher frequency side than the carrier centerfrequency, the relationship between the carrier center frequency andvalid SS block center frequency candidate can be obtained based on arule in a certain embodiment. Then UE can derive the location of carriercenter frequency based on the detected center frequency for SS block.So, ┌log₂ k┐ bits can be used for indication. Alternatively, the offsetbetween carrier center frequency and SS block carrier frequency can beindicated in terms of number of RB size.

Method 2: In a given carrier, there can be more than one valid SS blockcenter frequency candidates. There are some pre-defined restrictions onthe valid SS block center frequency candidates in the carrier.

Embodiment 1: One restriction of the valid SS block center frequencycandidates can be that at least the SS block transmission is not out ofthe carrier BW, which can be expressed by

${{{f_{{ch},n} - f_{{sync},m}}} \leq \frac{{BW_{carrier}} - {BW_{SS}}}{2}},$

where BW_(carrier) is the carrier BW, or can be considered the actualtransmission BW considering any possible guard band in the edge sides ofthe carrier, BW_(SS) is the BW of the SS block. f_(ch,n) is the carriercenter frequency determined by the gNB, and f_(sync,m) is the validcandidate for SS block center frequency.

Embodiment 2: Additional restriction of the valid SS block centerfrequency candidates can be the additional alignment in the frequencyresource grid in the carrier. For example, the resource grid in thefrequency domain can be determined based on the carrier centerfrequency, subcarrier spacing, and RB size, and so on. Given a carriercenter frequency determined by gNB, the valid SS block center frequencycandidates can be restricted to the ones aligned with a certain resourcegrid, e.g., aligned with the RB boundary or RB center in the carrier.When aligned with RB boundary, the condition can be expressed bymod(|f_(ch,n)−f_(sync,m)|,BW_(RB))=0 where BW_(RB) is the RB size withthe subcarrier spacing used in the SS block, f_(ch,n) is the carriercenter frequency determined by the gNB, and f_(sync,m) is the validcandidate of SS block center frequency.

Embodiment 3: One restriction of the valid SS block center frequencycandidates can be that only a subset of SS block center frequencysatisfying a pre-defined rule. For example, the subset can becompromised by the L valid SS block center frequency candidates, whichare closest to the carrier center frequency. Or, the subset can becompromised by the L valid candidate center frequency for thesynchronization signals, where the two neighbor candidates has apre-defined separation, e.g., a pre-defined integer times of channelraster size, or RB size, etc. The size of L can be pre-defined, ordepend on the system bandwidth.

Embodiment 4: The combination of the above conditions, e.g., inEmbodiment 1 and 2 and other conditions and restrictions can also beconsidered. The pre-defined conditions are known to both gNB and UE.

In method 2, the number of valid center frequency candidates for SSblock may be determined by the carrier BW, channel raster size, and RBsize, etc. Assuming that the channel raster is fixed at least in a givenfrequency band, and RB size is known to the UE based on detection of SSblock, the UE at least needs to know the BW information and hence toknow how many valid center frequency candidates for SS block. Then, theselected valid candidate can be indicated to the UE. The number of validcenter frequency candidates affects the indication overhead.

Regardless of the difference between the channel raster size andsynchronization raster size, if there are multiple overlapped carriers,e.g., a wideband carrier and a narrowband carrier coexist and overlap inthe frequency domain, one SS block may be transmitted and the SS blockcan be used as a shared SS block for a wideband carrier and a narrowbandcarrier. Based on the pre-defined rule, the location of a valid centerfrequency SS block candidate needs to satisfy the condition andrestriction for both the wideband carrier and the narrowband carrier.

FIG. 14A shows an example of a valid SS block candidate center frequencyfor both a narrowband carrier and a wideband carrier.

As shown in FIG. 14A, the SS block is transmitted in the 1^(st)candidate SS block center frequency which is a valid one in thenarrowband carrier, as well as a valid one in the wideband carrier.

FIG. 14B shows another example of valid SS block candidate centerfrequency for both narrowband carrier and wideband carrier.

As shown in FIG. 14B, one SS block is transmitted in the 1^(st)candidate SS block center frequency which is a valid one in thenarrowband carrier #0, as well as a valid one in the wideband carrier.Another block is transmitted in the 3^(rd) candidate SS block centerfrequency which is a valid one in the narrowband carrier #1, as well asa valid one in the wideband carrier.

C. Indication Methods to Derive SS Block Location and Carrier CenterFrequency

In different cases, based on the pre-defined rule, there may bedifferent possibilities of SS block center frequency candidates. Toenable UE obtain the information of carrier, e.g., carrier edge orcenter frequency, gNB may need to send indication related to the SSblock center frequency and/or carrier center frequency.

Case with Same Size of Channel Raster and the Synchronization Raster

In case that the size of channel raster and the synchronization rasteris the same, i.e., Δf_(sync_raster)=Δf_(ch_raster), the followingindication methods can be considered.

Method 1: If there is one valid SS block center frequency candidate in acarrier, there is no need of explicit indication and UE may derive thecarrier center frequency in an implicit manner based on the fixedrelationship between the carrier center frequency and SS block centerfrequency.

Method 2: Given a number of valid SS block center frequency candidatesin a carrier, e.g., N, ┌log₂N┐ bits can be used to indicate thepossibilities, each corresponding one valid candidate. Based on therelationship between the carrier center frequency and valid SS blockcenter frequency candidates, the information of carrier center frequencycan be derived. The number of candidates N may depend on the systembandwidth, channel raster size, RB size and so on. Assuming that thechannel raster is fixed at least in a given frequency band, and RB sizeis known to the UE based on detection of SS block, the number ofcandidates N may depend on the BW information. Therefore, the number ofcandidates N and required indication bits can be determined by the BWindication.

Method 3: Given a number of valid SS block center frequency candidatesin a carrier, e.g., N, there can be one bit field to indicate if the SSblock center frequency and the carrier center frequency satisfy apre-defined relationship. An example relationship is that the SS blockcenter frequency is the same as the carrier center frequency. If thefield is indicated as true, that means the pre-defined relationship issatisfied, the location of carrier center frequency can be implicitlyderived from the SS block center frequency, and there is no need offurther indication. Otherwise, i.e., the field is indicated as false,another field may further indicate the information of valid SS blockcenter frequency candidate in the carrier. As in Method 2, ┌log₂N┐ bitscan be used to indicate the possibilities. Or, by precluding the carriercenter frequency, the remaining number of valid center frequencycandidates for SS block in a carrier is N−1, and ┌log₂ (N−1)┐ bits canbe used to indicate the possibilities, each corresponding one validcandidate. Based on the relationship between the carrier centerfrequency and valid SS block center frequency candidates, theinformation of carrier center frequency can be derived.

Method 4: If the SS block center frequency has a certain restriction onthe RB boundary alignment, an index of a reference RB occupied by the SSblock can be indicated. The location of the reference RB has a fixedrelationship with the SS block. For example, the reference RB can be theRB closest to the center of SS block in a certain frequency side (higheror lower). Or, the reference RB can be the RB in the lower frequencyedge side of the SS block. The RB index in the full system bandwidth canbe signaled, e.g., by ┌log₂N_(RB) ^(DL)┐ bits. N_(RB) ^(DL) is themaximum number of RBs in the downlink carrier bandwidth based on thenumerology of SS block. Or, a function of the RB index can be signaled.This can provides the location of SS block in terms of occupied RBs, andthe carrier center frequency can be implicitly derived based in RBlocation of SS block and full system bandwidth information. When thesystem BW information is not available, e.g., not signaled in systeminformation, the UE can at least derive the location of lowest frequencyside of the carrier.

If the SS block center frequency has no restriction on the RB boundaryalignment, the SS block is not exactly aligned with the actual RB grid.

FIG. 15 shows an example of arbitrary subcarrier level offset between SSblock RB grid and actual system RB grid.

Referring to FIG. 15, there can be arbitrary offset of 0 to 11subcarriers between the SS block RB grid and actual system RB grid. So,one RB in a SS block may span two RBs of the actual RB grid.

FIG. 16 shows an example of misalignment between SS block RB grid andactual system RB grid.

For example in FIG. 16, The lower frequency side RB in the SS block span3 subcarriers in a RB with index N and 4 subcarriers in a RB with indexN+1. The subcarrier offset needs to be further indicated, e.g., by 4bits. The offset can be defined by the difference in terms of number ofsubcarriers between the lowest subcarrier in the SS block and theadjacent lower subcarrier of the actual RB in the lower frequency side.The offset can be defined by other rules. The subcarrier offset can beindicated in the MIB, and hence UE can derive actual RB grid afterreceiving SS block, and then get further information such as offset orRB index of SS block in RMSI.

Depending on the case if SS block is always aligned with RB boundary ornot, or may align with RB boundary in some situations, e.g., dependingon the frequency range or raster size cases, the subcarrier offset canbe always indicated, which make common MIB contents for all cases. Or,the subcarrier offset can be indicated depending on the conditions ifthe subcarrier offset is needed, e.g., not needed in lower frequencyranges, or needed in higher frequency ranges. So this may result indifferent MIB contents.

Method 5: The can be one bit field to indicate if the SS block centerfrequency and the carrier center frequency satisfy a pre-definedrelationship. An example relationship is that the SS block centerfrequency is the same as the carrier center frequency. If the field isindicated as true, that means the pre-defined relationship is satisfied,the location of carrier center frequency can be implicitly derived fromthe SS block center frequency, and there is no need of furtherindication. Otherwise, i.e., the field is indicated as false, anotherfield may further indicate the information of valid SS block centerfrequency candidate in the carrier. As in Method 4, an index of areference RB occupied by the SS block can be indicated. The RB index inthe full system bandwidth is signaled, e.g., by ┌log₂N_(RB) ^(DL)┐ bits.

Case with Different Size of Channel Raster and the SynchronizationRaster

In case that the size of channel raster and the synchronization rasteris different, assuming Δf_(sync_raster)=k×Δf_(ch_raster), where k is apre-defined positive integer number, the following indication methodscan be considered.

Method 1: Assuming that there is one valid SS block center frequencycandidate in a carrier, and location of the center frequency candidatecan be determined by knowing the relative distance between the carriercenter frequency and surrounding SS block center frequency candidates.For example, this relative distance can be expressed by

$\frac{{mod}\ \left( {f_{{ch},n},{\Delta\; f_{sync\_ raster}}} \right)}{\Delta\; f_{ch\_ raster}},$

which have k possibilities, {0, 1, 2, . . . , k−1}, and can be indicatedby ┌log₂ k┐ bits. The indication can be interpreted as the relativedistance between the carrier center frequencies to a reference centerfrequency candidate for SS block. Based on the relationship between thecarrier center frequency and valid SS block center frequency candidate,the information of carrier center frequency can be derived.

Method 2: If there is one valid SS block center frequency candidate in acarrier, there can be one bit field to indicate if the SS block centerfrequency and the carrier center frequency satisfy a pre-definedrelationship, e.g., the SS block center frequency is the same as thecarrier center frequency. If the field is indicated as true, that meansthe pre-defined relationship is satisfied, the location of carriercenter frequency can be implicitly derived from the SS block centerfrequency, and there is no need of further indication. Otherwise, i.e.,the field is indicated as false, another field may further indicate thek possibilities by ┌log₂ k┐ bits. Or, the following field may) indicatethe remaining (k−1) possibilities by ┌log₂ (k−1)┐ bits if thepre-defined relationship in the one bit field is that the SS blockcenter frequency is the same as the carrier center frequency.

Method 3: Given a number of valid SS block center frequency candidatesin a carrier, e.g., N, ┌log₂N┐ bits can be used to indicate thepossibilities, each corresponding to one valid candidate. The relativedistance between the carrier center frequency and surrounding centerfrequency candidates for SS block with ┌log₂ k┐ bits needs to beindicated together. Based on the relationship between the carrier centerfrequency and valid SS block center frequency candidates, theinformation of carrier center frequency can be derived. The number ofvalid candidates N may depend on the system bandwidth, channel rastersize, RB size and so on. Assuming that the channel raster size andsynchronization raster size are fixed at least in a given frequencyband, and RB size is known to the UE based on detection of SS block, thenumber of valid candidates N may depend on the BW information.Therefore, the number of candidates N and required indication bits canbe determined by the BW indication. The combined cases of multiplerelative distance between the carrier center frequency and surroundingcenter frequency candidates for SS block and multiple valid SS blockcenter frequency candidates can be jointly indicated, e.g., with┌log₂Nk┐ bits.

Method 4: Given a number of valid SS block center frequency candidatesin a carrier, e.g., N, there can be one bit field to indicate if the SSblock center frequency and the carrier center frequency satisfy apre-defined relationship, e.g., the SS block center frequency is thesame as the carrier center frequency. If the field is indicated as true,that means the pre-defined relationship is satisfied, the location ofcarrier center frequency can be implicitly derived from the SS blockcenter frequency, and there is no need of further indication. Otherwise,another field may further indicate the valid candidate by ┌log₂N┐ bits.The relative distance between the carrier center frequency andsurrounding center frequency candidates for SS block with ┌log₂ k┐ bitsneeds to be indicated together. The combined cases of multiple relativedistance between the carrier center frequency and surrounding centerfrequency candidates for SS block and multiple valid SS block centerfrequency candidates can be jointly indicated, e.g., with ┌log₂Nk┐ bits.

Method 5: If the SS block center frequency has a certain restriction onthe RB boundary alignment, an index of a reference RB occupied by the SSblock can be indicated. The location of the reference RB has a fixedrelationship with the SS block. For example, the reference RB can be theRB closest to the center of SS block in a certain frequency side (higheror lower). The RB index in the full system bandwidth can be signaled,e.g., by ┌log₂N_(RB) ^(DL)┐ bits. N_(RB) ^(DL) is the number of RBs inthe downlink carrier bandwidth based on the numerology of SS block. Or,a function of the RB index can be signaled. This can provides thelocation of SS block in terms of occupied RBs, and the carrier centerfrequency can be implicitly derived based in RB location of SS block andfull system bandwidth information. When the system BW information is notavailable, e.g., not signaled in system information, the UE can at leastderive the location of lowest frequency side of the carrier.

If the SS block center frequency has no restriction on the RB boundaryalignment, the SS block is not exactly aligned with the actual RB grid.For example in FIG. 16, one RB in a SS block may span two RBs of theactual RB grid. The lower frequency side RB in the SS block span 3subcarriers in a RB with index N and 4 subcarriers in a RB with indexN+1. The subcarrier offset needs to be further indicated, e.g., by 4bits. The offset can be defined by the difference in terms of number ofsubcarriers between the lowest subcarrier in the SS block and theadjacent lower subcarrier of the actual RB in the lower frequency side.The offset can be defined by other rules. The subcarrier offset can beindicated in the MIB, and hence UE can derive actual RB grid afterreceiving SS block, and then get further information such as offset orRB index of SS block in RMSI.

Similarly, depending on the case if SS block is always aligned with RBboundary or not, or may align with RB boundary in some situations, e.g.,depending on the frequency range or raster size cases, the subcarrieroffset can be always indicated, which make common MIB contents for allcases. Or, the subcarrier offset can be indicated depending on theconditions if the subcarrier offset is needed, e.g., not needed in lowerfrequency ranges, or needed in higher frequency ranges. So this mayresult in different MIB contents.

Method 6: There can be one bit field to indicate if the SS block centerfrequency and the carrier center frequency satisfy a pre-definedrelationship, e.g., the SS block center frequency is the same as thecarrier center frequency. If the field is indicated as true, that meansthe pre-defined relationship is satisfied, the location of carriercenter frequency can be implicitly derived from the SS block centerfrequency, and there is no need of further indication. Otherwise, i.e.,the currently detected SS block center frequency is not the carriercenter frequency; another field may further indicate the information ofvalid SS block center frequency candidate in the carrier. As in Method5, an index of a reference RB occupied by the SS block can be indicated.The RB index in the full system bandwidth can be signaled, e.g., by┌log₂N_(RB) ^(DL)┐ bits.

The number of valid SS block center frequency candidates in a carrier isaffected by many factors, e.g., channel raster size, synchronizationraster size, and rules of determining the valid SS block centerfrequency candidates, such as RB size, BW, etc. In different frequencybands, the channel raster size may be different, the synchronizationraster size may be different and the supported carrier BW and RB sizemay also be different. Based on the pre-defined rule, there aredifferent possibilities of SS block center frequency candidates, anddifferent indication methods may be used in different cases.

FIG. 17 is a flowchart of gNB procedure to determine SS block centerfrequency and make indication to UE.

Referring to FIG. 17, gNB determines frequency range for a carrierdeployment at operation 1710. The gNB decides carrier center frequencybased on channel raster size requirement and carrier BW at operation1720. The gNB checks number and location of valid SS block centerfrequency candidates within the carrier based on the pre-define rule atoperation 1730. If there is more than one valid SS block centerfrequency candidates, the gNB selects one valid SS block centerfrequency candidate for SS block transmission at operation 1740, andindicates information related to the selected SS block center frequencycandidate and/or carrier center frequency at operation 1750. Otherwise,i.e., if there is only one valid SS block center frequency candidate,the gNB decides the valid block center frequency candidate for SS blocktransmission at operation 1760. If any indication is needed, the gNBindicates information related to the selected SS block center frequencycandidate and/or carrier center frequency at operation 1750. Otherwise,i.e., if there is no need of any indication, the gNB does not makeindication to UE at operation 1770.

FIG. 18 is a flowchart of UE procedure to search SS block centerfrequency and derive carrier center frequency.

Referring to FIG. 18, UE determines a frequency range for searching thecarrier at operation 1810. The UE searches the synchronization signalsbased on synchronization raster size requirement in the frequency rangeat operation 1820. The UE detects synchronization signals and receivessystem information in MIB carried by PBCH and/or RMSI (e.g. SIB1) atoperation 1830. The UE checks number of valid SS block center frequencycandidates within the carrier based on the pre-defined rule at operation1840. If there is more than one valid SS block center frequencycandidates, the UE obtains indication related to the selected SS blockcenter frequency candidate and carrier center frequency at operation1850, and derives actual location of SS block center frequency andcarrier center frequency based on pre-defined rule at operation 1860.Otherwise, i.e., if there is only one valid SS block center frequencycandidate, the UE determines whether there is any indication atoperation 1870. If there is any indication, the UE obtains indicationrelated to the selected SS block center frequency candidate and carriercenter frequency at operation 1850, and derives actual location of SSblock center frequency and carrier center frequency based on pre-definedrule at operation 1860. Otherwise, i.e., if there is no indication, theUE derives actual location of SS block center frequency and carriercenter frequency based on pre-defined rule at operation 1880.

Assume that the synchronization signals (PSS/SSS) and PBCH have the samecenter frequency and the SS block center frequency may be different fromthe carrier center frequency, the information related to the SS blockcenter frequency and carrier center frequency can be indicated in theMIB, or RMSI, or both MIB and RMSI, e.g., partial information in MIB andpartial information in RMSI. Together with the system bandwidthinformation, the frequency resources occupied by the carrier can beobtained.

FIG. 19 shows an example of carrier center frequency indication in MIB.

In the example of FIG. 19, the carrier center frequency can be derivedbased on the indication in MIB.

FIG. 20 shows an example of carrier center frequency indication in RMSI.

In the example of FIG. 20, the carrier center frequency can be derivedbased on the indication in RMSI.

Indication in MIB

In the MIB, the information related to the SS block center frequency andcarrier center frequency can be indicated. In a given frequency range,the size of channel raster and synchronization raster is pre-defined.The indication related to the SS block center frequency and carriercenter frequency may or may not depend on the system bandwidth, e.g.,may only depend on the relationship between the size of channel rasterand synchronization raster.

In a given frequency range, if the indication related to the SS blockcenter frequency and carrier center frequency does not depend on thesystem bandwidth, the number of indication bit can be pre-defined. Ifthe indication related to the SS block center frequency and carriercenter frequency depends on the system bandwidth, the number ofindication bits can be pre-defined as well to keep the common signalingformat in a given frequency range. Or, the indication can be related tothe system bandwidth.

FIG. 21 shows an example of BW dependent indication of SS block locationin MIB.

As shown in FIG. 21, given an indicated system bandwidth, the followingindication can be different. For example for some small BW cases, thereis one valid SS block center frequency candidate having fixedrelationship with the carrier center frequency, and hence there is noindication related to the valid SS block center frequency. In case ofother system bandwidth options, there can be more than one valid SSblock center frequency candidates, or one valid SS block centerfrequency candidates but the relative indication is still needed (e.g.,larger synchronization raster size case), there is indication field tosignal the information related to the SS block center frequency andcarrier center frequency. The indication can be jointly coded with otherparameters.

In case that the SS block may not be aligned with the actual system RBgrid, the subcarrier offset needs to be indicated in MIB, e.g., by 4bits.

After receiving MIB in PBCH and obtain carrier center frequency andsystem BW information, the succeeding UE operation can be based on thefull system BW, e.g., to receive the PDCCH and RMSI.

Indication in RMSI

In the RMSI, the information related to the SS block center frequencyand carrier center frequency can be indicated. The similar indicationapproaches can be used for indication.

After receiving MIB in PBCH, if there is no related indication ofcarrier center frequency and system BW, the succeeding UE operationcannot be based on the full system BW. For example, to receive the PDCCHand RMSI, the UE may need to assume the same BW with the SS block. Afterreceiving RMSI and obtaining carrier center frequency and system BWinformation, the succeeding UE operation can be based on the full systemBW, e.g., to receive the other system information.

Indication in Both MIB and RMSI

In the MIB, partial information related to the SS block center frequencyand carrier center frequency can be indicated. For example in MIB, thesystem BW can be indicated, and there can be 1 bit flag field toindicate if the SS block center frequency and the carrier centerfrequency satisfy a pre-defined relationship, e.g., the SS block centerfrequency is the same as the carrier center frequency. If the field isindicated as true, that means the pre-defined relationship is satisfied,the location of carrier center frequency can be implicitly derived fromthe SS block center frequency, and there is no need of furtherindication in both MIB and RMSI. Otherwise, the further information ofrelationship of current SS block center frequency and carrier centerfrequency is indicated in RMSI. This can minimize the overhead in MIB.The 1 bit flag indication can always exist to enable a common MIB formatat least for a given frequency range. Similarly, the existence of 1 bitflag indication in MIB may depend on the cases. 1 bit flag indicationcan be BW dependent indication. For example for some small BW cases,there is one valid SS block center frequency candidate having fixedrelationship with the carrier center frequency, and hence there is noindication. In case of other system bandwidth options, there can be morethan one valid SS block center frequency candidates, or one valid SSblock center frequency candidates but the relative indication is stillneeded (e.g., larger synchronization raster size case), there is 1 bitflag indication. The indication can be jointly coded with otherparameters.

After receiving MIB in PBCH, the UE can know if the carrier centerfrequency is the same as the SS block center frequency or not. If thesame, based on the system BW information, the succeeding UE operationcan be based on the full system BW, e.g., to receive the PDCCH and RMSI.If not, the succeeding UE operation cannot be based on the full systemBW. For example, to receive the PDCCH and RMSI, the UE may need toassume the same BW with the SS block. After receiving RMSI and obtaincarrier center frequency and system BW information, the succeeding UEoperation can be based on the full system BW, e.g., to receive the othersystem information.

FIGS. 22A and 22B are a flowchart of gNB procedure to determine SS blockcenter frequency and make indication to UE.

Referring to FIG. 22A, gNB determines frequency range for a carrierdeployment at operation 2210. The gNB decides carrier center frequencybased on channel raster size requirement and carrier BW at operation2220. The gNB checks number and locations of valid SS block centerfrequency candidates within the carrier based on the pre-define rule atoperation 2230. If there is more than one valid SS block centerfrequency candidates, the gNB selects one valid SS block centerfrequency candidate for SS block transmission at operation 2240.Otherwise, i.e., if there is only one valid SS block center frequencycandidate, the gNB decides the valid block center frequency candidatefor SS block transmission at operation 2250.

Referring to FIG. 22B, if there is no need of any indication, the gNBdeciding the valid SS block center frequency candidate for SS blocktransmission at operation 2250, does not make indication to UE atoperation 2260. If any indication is needed or the gNB selects one validSS block center frequency candidate for SS block transmission atoperation 2240, the gNB determines whether the SS block center frequencyand the carrier center frequency satisfy a pre-defined relationship atoperation 2270. If the SS block center frequency and the carrier centerfrequency satisfy the pre-defined relationship, the gNB indicates as‘True’ about pre-defined relationship of SS block center frequency andcarrier center frequency in MIB at operation 2280, and there is noadditional indication in MIB an RMSI at operation 2285. Otherwise, i.e.,the SS block center frequency and the carrier center frequency does notsatisfy the pre-defined relationship, the gNB indicates as ‘False’ aboutpre-defined relationship of SS block center frequency and carrier centerfrequency in MIB at operation 2290, and indicates information related tothe selected SS block center frequency candidate and/or carrier centerfrequency at operation 2295.

FIG. 23 is a flowchart of UE procedure to search SS block centerfrequency and derive carrier center frequency.

Referring to FIG. 23, UE determines a frequency range for searching thecarrier at operation 2310. The UE searches the synchronization signalsbased on synchronization raster size requirement in the frequency rangeat operation 2320. The UE detects synchronization signals and receivessystem information in MIB carried by PBCH at operation 2330. The UEdetermines whether there is a flag indication in the system informationat operation 2340. If there is no flag indication or the flag indicationin the system information indicates ‘True’ about pre-definedrelationship of SS block center frequency and carrier center frequency,the UE derives actual location of SS block center frequency and carriercenter frequency based on pre-defined rule at operation 2350. If theflag indication in the system information indicates ‘False’ aboutpre-defined relationship of SS block center frequency and carrier centerfrequency, the UE receives system information in RMSI (e.g. SIB1) basedon configuration in MIB at operation 2360, obtains indication related tothe selected SS block center frequency candidate and carrier centerfrequency at operation 2370, and derives actual location of SS blockcenter frequency and carrier center frequency based on pre-defined ruleat operation 2380.

In some cases, the information related to the SS block center frequencyand carrier center frequency can be indicated in the other SIBs. Thesimilar indication approaches can be used for indication. Theinformation related to the SS block center frequency and carrier centerfrequency can be indicated to UEs via RRC configuration.

Multi-Carrier Shared SS Block Case

If a SS block is linked to more than one carrier, e.g., one widebandcarrier and one narrowband carrier, the related information of SS blockcenter frequency and carrier frequency can be indicated per carrier.

In one embodiment, the information of the number of carriers and theinformation of the SS block center frequency and carrier frequency percarrier can be indicated in the RMSI and/or other SIBs. For example,there can be a restriction that a SS block can be shared by a maximum ofK carriers, where K is a pre-defined value.

In the related indication field, there can be a first field to indicatethe number of carriers linked to the SS block, and then the followingindications can be per carrier. In the indication for each carrier, aset of related parameters can be indicated. For example, the DL carrierBW and/or the paired carrier BW (e.g., in frequency division duplex(FDD) case) can be indicated. In addition, the information of the SSblock center frequency and carrier frequency can be indicated. Forexample, the offset between the carrier center frequency and the SSblock center frequency can be indicated, in terms of number of physicalresource block (PRBs) with a pre-defined numerology, e.g., thenumerology used by the SS block. Or, the index of one reference RBrelated to the SS block can be indicated. For example, the reference RBcan be the RB closest to the center of SS block in a certain frequencyside (higher or lower). The RB index in the full system bandwidth can besignaled, e.g., by ┌log₂N_(RB) ^(DL)┐. N_(RB) ^(DL) is the number of RBsin the downlink carrier bandwidth based on the numerology of SS block,or another pre-defined numerology which is specific to the frequencyband. Or, a function of the RB index can be signaled. This can providesthe location of SS block in terms of occupied RBs, and the carriercenter frequency can be implicitly derived based in RB location of SSblock and full system bandwidth information. Since the indications areconveyed in the RMSI and/or SIBs, all UEs can obtain the carrierinformation and SS block information. The network may configure a UE tooperate in a certain carrier, e.g., a wideband carrier or a narrowbandcarrier. The configuration can be signaled to UE by RRC.

FIG. 24 shows an example of a network configuring a carrier index to theUE.

Since the carrier related information is indicated in RMSI and/or SIBs,the network configure a carrier index to the UE, as shown in the examplein FIG. 24.

FIG. 25 is a flowchart of UE to obtain information of multiple carriersand carrier assigned to the UE.

Referring to FIG. 25, UE determines a frequency range for searching thecarrier at operation 2510. The UE searches the synchronization signalsbased on synchronization raster size requirement in the frequency rangeat operation 2520. The UE detects synchronization signals and receivessystem information in MIB carried by PBCH and/or RMSI (e.g. SIB1) atoperation 2530. The UE receives information of carriers linked to thedetected SS block in RMSI and/or SIBs at operation 2540. The UE obtainsconfiguration of assigned carrier from RRC signaling if there aremultiple carriers at operation 2550. The UE derives actual location ofSS block center frequency and carrier center frequency based onpre-defined rule at operation 2560.

In another case, the information of all carriers is not signaled in theRMSI and/or SIB, the network signals the UE-specific carrier informationin RRC. Similarly, the information of the carrier bandwidth, andinformation related to the SS block center frequency and carrier centerfrequency can be indicated.

Single Carrier with Multiple SS Blocks

It is possible that multiple SS blocks can be transmitted in a carrier,e.g., in a wideband carrier case. Each SS block may correspond to itsown RMSI and SIBs.

FIGS. 26, 27 and 28 illustrate multiple SS blocks in a single carrier.

As shown in FIG. 26, there is a Set #0 of SS block #0 and correspondingRMSI and/or SIBs, and there is another Set #1 of SS block #1 andcorresponding RMSI and/or SIBs. If the carrier information is signaledin RMSI and/or SIBs, it can be transmitted individually in each set ofRMSI and/or SIBs, e.g., about carrier BW and information of the SS blockcenter frequency and carrier center frequency. Due to the differentlocation of different SS blocks, the information can be different indifferent RMSI and/SIBs. In addition, the presence of other SS blocksand related transmission information of RMSI and/or SIBs can beindicated in the RMSI and/SIBs. That means, in RMSI and/or SIBs in Set#0, the information of SS block #0 is signaled. In addition, theinformation of SS block #1 and corresponding Set #1 of RMSI and/or SIBsis signaled as well. The cell ID of SS block #1 can be indicated. Afterobtaining the information of resources occupied by all the SS blocks andRMSI/SIBs, these resources may not be used for data transmission. Forexample, the UE may assume that the resources are rate matched if thereare data transmissions assigned to UE.

In some case, one SS block has its own RMSI and SIBs while another SSblock may not have corresponding RMSI and/or SIBs, as shown in FIG. 27.In this case, the RMSI and/or SIBs indicates that the presence of otherSS block only, and indicate that there is not corresponding RMSI and/orSIBs transmission. In another case, the signals (PSS/SSS) and channels(PBCH) in a SS block may be not all transmitted. For example, only thePSS/SSS is transmitted in a certain SS block, and there is no PBCH andRMSI/SIB transmission. This can be considered as a thin SS block, whichis transmitted for certain purpose only, e.g., for measurements. Theinformation of the presence of a thin SS block and the components in theSS block can be indicated.

In another case, multiple SS blocks may have shared RMSI and SIBs, asshown in FIG. 28. The information of all SS blocks can be indicated inthe RMSI and/or SIBs.

FIG. 29 is a flowchart of UE to obtain information of multiple SSblocks.

Referring to FIG. 29, UE determines a frequency range for searching thecarrier at operation 2910. The UE searches the synchronization signalsbased on synchronization raster size requirement in the frequency rangeat operation 2920. The UE detects synchronization signals and receivessystem information in MIB carried by PBCH at operation 2930. The UEdetermines whether there is an associated RMSI indicated in MIB atoperation 2940. If there is an associated RMSI indicated in MIB, the UEobtains indication related to the carrier and SS blocks in RMSI and/orSIBs at operation 2950, derives actual location of detected SS blockcenter frequency and carrier center frequency based on pre-defined ruleat operation 2960, and derives information of other SS blocks and/orrelated RMSI/SIB resource for other purposes at operation 2970.

Extended Combinations

In some case, one SS block may be shared by multiple carriers, and therecan be multiple SS blocks transmitted in a certain carrier, e.g., in awideband carrier case.

FIG. 30 illustrates multiple SS blocks transmitted in a widebandcarrier.

This is the combination case of the previous cases. As described, eachSS block may correspond to its own RMSI and SIBs. The carrierinformation is signaled in the RMSI and/or SIBs. In addition, for eachcarrier, the presence of multiple SS block and/or RMSI and/or SIBs issignaled. This includes the case that a certain SS block may not havethe corresponding RMSI and/or SIBs, or a certain SS block is a kind ofthin SS block and only part of the signals (PSS/SSS) and/or channels(PBCH) is transmitted.

In another case, multiple SS blocks may have shared RMSI and SIBs, asshown in FIG. 30. The information of all carriers and SS blocks can beindicated in the RMSI and/or SIBs.

D. RMSI Reception RMSI Numerology Indication in MIB

Assume that the system supports multiple subcarrier spacing values,e.g., Δf₀, Δf₁, Δf₂, Δf₃, . . . , Δf_(N−1) (where Δf_(n)<Δf_(n+1),0≤n<N−1); the usage of certain subcarrier spacing may depend on theservice and system requirement, as well as the frequency range. Toreduce the complexity in the initial access, the subcarrier spacing forSS block can be pre-defined or selected by gNB from the full set or asubset of the supported subcarrier spacing values. The same subcarrierspacing can be used for synchronization and PBCH transmission. However,the subcarrier spacing for control channel (PDCCH) scheduling RMSItransmission can be different from the subcarrier spacing used forsynchronization and PBCH transmission. Hereafter the control channel(PDCCH) scheduling RMSI transmission means the RMSI control resource set(CORESET) which includes a set of RBs and symbols to convey the PDCCHwhich schedules RMSI.

The subcarrier spacing used for RMSI CORESET for PDCCH scheduling RMSItransmission can be indicated in the payload of PBCH, i.e., MIB. TheRMSI PDCCH and RMSI PDSCH can have the same subcarrier spacing. Thefollowing indication methods can be used:

Option 1: Implicit indication of the PDCCH subcarrier spacing, whichmeans there may be no indication and the same numerology with PBCH isused for PDCCH subcarrier spacing.

Option 2: Explicitly indicating the PDCCH subcarrier spacing among apre-defined subcarrier spacing subset. For example, the full set ofsubcarrier spacing can be divided into multiple subsets, eachcorresponding to a certain frequency range, e.g., one pre-defined subsetfor lower frequency bands (e.g., below-6 GHz frequency band) and anotherpre-defined subset for higher frequency bands (e.g., above-6 GHzfrequency band). Since the subcarrier spacing used by synchronizationand PBCH may be different for different frequency bands, there can beseveral pre-defined subcarrier spacing subsets, and each subsetcorresponds to one subcarrier spacing used by the synchronization andPBCH. The number of subcarrier spacings in each subset can be different,and hence may have different number of signaling bits, depending on thefrequency range, or subcarrier spacing used by the synchronization andPBCH. The following examples can be considered:

1) SS block subcarrier spacing (SCS)=15 kHz→RMSI numerology can be 15kHz or 30 kHz or 60 kHz based on indication

2) SS block SCS=30 kHz→RMSI numerology can be 15 kHz or 30 kHz or 60 kHzbased on indication

3) SS block SCS=120 kHz→RMSI numerology can be 60 kHz or 120 kHz or 240kHz based on indication

4) SS block SCS=240 kHz→RMSI numerology can be 60 kHz or 120 kHz or 240kHz based on indication

So 2 bits can be used to indicate up to 4 possibilities of used RMSInumerology.

Option 3: There can be 1 bit indication to indicate if the subcarrierspacing used for PDCCH is the same as that used by SS block or apre-defined different subcarrier spacing is used for PDCCH. Or, in casethat the subcarrier spacing of SS block may not be used for control anddata transmission, two other subcarrier spacings can be used forindication. The following examples can be considered:

1) SS block SCS=15 kHz→RMSI numerology can be 15 kHz or 30 kHz based onindication

2) SS block SCS=30 kHz→RMSI numerology can be 30 kHz or 60 kHz based onindication

3) SS block SCS=120 kHz→RMSI numerology can be 60 kHz or 120 kHz basedon indication

4) SS block SCS=240 kHz→RMSI numerology can be 60 kHz or 120 kHz basedon indication (e.g., in case that 240 kHz may not be used forcontrol/data transmission)

Option 4: Joint encoding of the numerology indication field with otherfield. In this option, the numerology indication and other fields can bejointly encoded, e.g., the location of the RMSI CORESET for PDCCH, andso on.

Some of the above options can be used together to for subcarrier spacingin the different cases. For example, in one frequency band case or onesubcarrier spacing case used by SS block, the same subcarrier spacingused by SS block is used for PDCCH. So there may be no need to indicatethe subcarrier spacing, i.e., derived implicitly. In another case,different subcarrier spacing may be used and hence explicit indicationis needed. The different indication case may require no indication bitor may require different number of indication bits, and hence theinterpretation of MIB contents in different cases, e.g., differentfrequency band case or different synchronization/PBCH subcarrier spacingcase, can be different.

RMSI Frequency Resource Indication in MIB

The RMSI can be scheduled by PDCCH and transmitted by PDSCH. Dependingon the amount of information of system BW and carrier center frequencyindicated in MIB, the UE may have different ways to receive RMSI. Thereare the following cases

1) The UE can obtain or derive system BW and carrier center frequencyfrom MIB

2) The UE does not know system BW and carrier center frequency from MIB

If the UE can obtain or derive the system BW and carrier centerfrequency from MIB, the PDCCH for RMSI monitoring (more generally acommon search space) can be mapped around the carrier center frequency,and the size of RMSI CORESET (PDCCH transmission) BW can be from the SSblock bandwidth to the full system bandwidth. The following methods canbe considered to indicate the RMSI CORESET BW for PDCCH monitoring:

Option 1: Pre-defined size without indication. Different sizes can beconsidered for different system BW cases or for different frequencybands. There is a linkage between a system BW in a certain frequencyband and the size of BW for PDCCH monitoring. For example, the size canbe X when the system BW is less than BW_i, and Y when the system BW islarger than BW_i but less than BW_j, and Z when the system BW is largerthan BW_j. The values of X, Y, Z and BW_i, BW_j can be pre-defined.

Option 2: The PDCCH transmission BW can be explicitly indicated. Thepossible BW options for PDCCH transmission can be pre-defined. Forexample, the BW options for PDCCH transmission can be selected from thesupported system BW cases and/or the supported UE BW case. The BW optionfor PDCCH transmission is explicitly indicated. The required number ofindication can be different for different BW cases.

Option 3: There can be one bit indication to inform that if the BW forPDCCH monitoring is the system BW and a pre-defined BW. An example isthat the pre-defined BW is the minimum UE BW to enable that all UEs canreceive the RMSI. The pre-defined BW can be different for differentsystem BW cases and different frequency bands.

Option 4: The PDCCH transmission BW can be related to the BW of the SSblock. Assuming that BW of the SS block is X, the indication can be afunctionality of the BW X, e.g., X, 2X, and so on. The functionality canbe different for different cases, e.g., in terms of system BW, and/orfrequency band, and so on. The BW can be expressed by the number of RBs,e.g., 24 RBs or 48 RBs or 96 RBs can be considered, since SS block has24 RBs.

Some of the above options can be used together to for determine thePDCCH transmission BW. For example, in one frequency band case or onesubcarrier spacing case used by synchronization and PBCH, no indicationof the PDCCH BW is needed and it is pre-defined. In another case,different PDCCH BW options may be used and hence explicit indication isneeded. The different indication case may require no indication bit ormay require different number of indication bits, and hence theinterpretation of MIB contents in different cases, e.g., differentfrequency band case or different synchronization/PBCH subcarrier spacingcase, can be different.

If the UE has no information of the system BW and carrier centerfrequency from MIB, the PDCCH for RMSI monitoring (more generally acommon search space) can be mapped around the SS block center frequency,and the size of PDCCH transmission BW can be restricted. The followingmethods can be considered to indicate the BW for PDCCH monitoring:

Option 1: Pre-defined size without indication. Different sizes can beconsidered for different SS block BW cases or for different frequencybands. There is a linkage between a SS block BW in a certain frequencyband and the size of BW for PDCCH monitoring.

Option 2: The PDCCH transmission BW can be explicitly indicated. Thepossible BW options for PDCCH transmission can be pre-defined. Forexample, the BW options for PDCCH transmission can be selected from thesupported minimum system BW cases, and/or the supported minimum UE BWcases, and/or SS block BW. The BW option for PDCCH transmission isexplicitly indicated. The required number of indication can be differentfor different SS block BW cases.

Option 3: There can be one bit indication to inform that if the BW forPDCCH monitoring is the SS block BW or another pre-defined BW. Anexample is that the pre-defined BW is the minimum UE BW to enable thatall UEs can receive the RMSI. The pre-defined BW can be different fordifferent system BW cases and different frequency bands.

Option 4: The PDCCH transmission BW can be related to the BW of the SSblock. Assuming that BW of the SS block is X, the indication can be afunctionality of the BW X, e.g., X, 2X, and so on. The functionality canbe different for different cases, e.g., in terms of system BW, and/orfrequency band, and so on. The BW can be expressed by the number of RBs,e.g., 24 RBs or 48 RBs can be considered, since SS block has 24 RBs.

The indication of BW of PDCCH monitoring may include the combinations ofthe options for PDCCH mapped around the carrier center frequency and theoptions for PDCCH mapped around the SS block center frequency. Or, 1 bitcan be first indicated that the PDCCH is mapped around the carriercenter frequency or the SS block center frequency. Then the followingfield further indicates the BW option for PDCCH monitoring.

If there is no restriction to always map the PDCCH location around thecarrier center frequency or the center frequency detected based onPSS/SSS/PBCH, the PDCCH transmission can be located in the system BW ina more flexible manner. The PDCCH location information needs to beadditionally signaled. The following PDCCH location information can besignaled.

Option 1: The offset between a reference location for PDCCH transmissionand a reference location of SS block can be signaled. For the SS block,the reference location can be the center of the SS block, or the RBwhich is closest to the SS block center, or the RB in the edge side ofthe SS block, e.g., the lower frequency edge side or the higherfrequency edge side. For example, the offset can be defined in terms ofPRBs with certain reference numerology, e.g., the one used by SS blockor the one used by PDCCH based on a pre-defined rule. Or, the smallernumerology (subcarrier spacing among SS block and indicated RMSI PDCCH)can be used as the reference numerology since it provides finergranularity. It helps to indicate the offset required for RB alignmentamong different subcarrier spacing cases. A number of pre-defined offsetcases can be signaled. For example, 2 bits can be used to indicate anoffset of {0, +1, −1, reserved} PRBs, compared to the center of SSblock. The reserved case can be used for other purpose, e.g., it mayindicate there is no RMSI transmission. Or, 2 bits can be used toindicate 4 different offset case, e.g., {0, 1, 2, 3} PRBs, compared tothe center of SS block. Depending on the number of required offsetcases, the number of signaling bits can be different.

Option 2: The offset between a reference location for PDCCH transmissionand a reference location of SS block can be implicitly derived based ona pre-defined function. For example, the offset in terms of RB can be afunction of the cell ID derived from PSS/SSS, e.g., offset=mod(Cell_ID,N)+M, where N and M are a pre-defined number. For example N can be 3,and M can be −1, which provides 3 different offset, can be used fordifferent sector cases. Other parameters can be used according to thesystem requirement.

In above Option 1, it is assumed that the SS block is at least alignedwith the RB grid of the subcarrier spacing used by the SS block.

FIGS. 31A, 31B and 31C are examples of indication of RMSI CORESETfrequency location.

As shown in FIG. 31A, the SS block occupy 24 RBs with subcarrier spacingf, and aligned with the RB grid of the subcarrier spacing f. Therefore,the SS block center is at least aligned with the RB grid of SS blocksubcarrier spacing f and lower subcarrier spacings, e.g., f/2. In caseof larger subcarrier spacing case, e.g., 2f, the center of SS block maynot align with the corresponding RB grid. It can be aligned with the RBboundary or located in the center of a RB. Therefore, the indicatedoffset with granularity of one PRB based on a smaller SCS can beconsidered as a way to enable RB alignment for RMSI CORESET. Thegranularity of one PRB based on SS block SCS is also possible. For RMSICORESET with smaller SCS, e.g., f/2, the offset can be based on thecorresponding SCS itself (which means the lower SCS between SS Block SCSand indicated RMSI CORESET SCS), as shown in in FIG. 31A. In this case,the granularity of indicated offset can be determined by the indicatedSCS for RMSI CORESET. Or, the offset can be always based on the SS blockSCS, as shown in in FIG. 31B. Depending on the supported RMSI CORESETSCS, the required number of offset cases can be different. For example,if there is possibility that the RMSI CORESET SCS can be 4 times of theSS block SCS, at least 4 offset cases need to be indicated to allow RBgrid alignment in all possible cases, as shown in FIG. 31C. In FIGS.31A, 31B and 31C, only some possible examples of RMSI CORESET SCS andoffset cases are shown. The offset cases can be pre-defined based on thesystem requirement, which is extendable by considering the rule, such asRB grid alignment among different subcarrier spacing cases.

FIG. 32 shows UE procedure to obtain RMSI CORESET frequency resourcelocation information.

Referring to FIG. 32, UE detects SS block at operation 3210. The UEdecodes MIB, and obtains information of RMSI SCS, frequency locationinformation and other related information at 3220. The UE determines thereference location and RB grid information of RMSI CORESET based on SCSand offset information at operation 3230. The UE determines fullinformation of CORESET frequency location based on bandwidth atoperation 3240.

To reduce the signaling overhead, the RMSI CORESET subcarrier spacingand frequency location can be jointly encoded. For example, when theRMSI CORESET subcarrier spacing is the same or less than the SS blocksubcarrier spacing, the offset can be 0. For the case that RMSI CORESETsubcarrier spacing is larger than the SS block subcarrier spacing, theoffset can be further indicated to allow RB alignment.

FIG. 33 shows an example of indication of limited cases of RMSI CORESETfrequency location.

Specifically, FIG. 33 shows the example where a subset of the possibleindication cases in FIGS. 31A, 31B and 31C is illustrated. So, 2 bitscan be used to indicate the subcarrier spacing and offset case jointly.

If it is not always the case that the SS block is aligned with RB grid,e.g., 24 RBs in a SS block can span 25 RBs with some offset of severalsubcarriers, the reference position can be defined within the 25 RBswhich contains SS block. The subcarrier offset can be separatelyindicated in MIB to enable UE know the actual RB grid given the SS blocksubcarrier spacing. So based on the detected SS block location, andindicated subcarrier offset between SS block and actual RB grid, the UEcan know the RB grid of the 25 RBs containing SS Block. The referencelocation to indicate offset of RMSI CORESET can be based on a certain RBlocation, e.g., the 13^(th) RB which is the RBs in the middle of 25 RBs,or the 1^(st) RB or 25^(th) RB in the edge side. The reference locationcan be referring to one side boundary of a reference RB or the center ofa reference RB, based on a pre-defined rule. The reference location ofRMSI CORESET can be determined by an offset from the reference locationof the SS block (25 RBs).

FIG. 34 shows another example of indication of RMSI CORESET frequencylocation.

As shown in the example of FIG. 34, the reference location of SS blockis the edge side of the 13^(th) RB in the 25 RBs containing SS-block,and the reference location of RMSI CORESET is its center. Based on theindicated offset in terms of RBs, the RMSI CORESET location can bederived. With the indicated or pre-defined CORESET BW, the frequencylocation of RMSI CORESET can be determined.

Similarly, to reduce the signaling overhead, the RMSI CORESET subcarrierspacing and frequency location can be jointly encoded. For example, whenthe RMSI CORESET subcarrier spacing is the same or less than the SSblock subcarrier spacing, the offset can be 0. For the case that RMSICORESET subcarrier spacing is larger than the SS block subcarrierspacing, the offset can be further indicated to allow RB alignment.

In the indication cases above, it mainly consider the cases that thecenter position of RMSI CORESET is close to the SS block center, withsome potential offset due to different numerology or unaligned RB grid.It is also possible to include other cases for possible RMSI CORESETlocations, e.g., frequency division multiplexing (FDM) with SS block.For example, the RMSI CORESET can be located in a set of RBs above theSS block or below the SS block.

FIGS. 35, 36 and 37 show examples of indication cases of RMSI CORESETfrequency location.

As shown in FIG. 35, there can be a further offset between the edges ofSS block and RMSI CORESET, e.g., 0 or 1 RBs to enable RB grid alignment.Since different numerologies may be FDMed, there is potentialinterference from each other. To consider this in the CORESET locationconfiguration, some guard band can be considered. For example in FIG.36, in case of larger subcarrier case, the offset can be 1 or 2 RBs toensure that at least 1 RB can be used as a guard band between SS Blockand RMSI CORESET in FDM case.

If it is not always the case that the SS block is aligned with RB grid,e.g., 24 RBs in a SS block can span 25 RBs with some offset of severalsubcarriers, the reference position can be defined within the 25 RBswhich contains SS block. Similarly, the reference location can be basedon a certain RB location, e.g., the 1^(st) RB or 25^(th) RB in the edgeside. The reference location can be referring to one side boundary of areference RB or the center of a reference RB, based on a pre-definedrule. The reference location of RMSI CORESET can be determined by anoffset from the reference location of the SS block (25 RBs), as shown inthe example of FIG. 37.

A set of the potential RMSI CORESET locations considering the abovecases can be indicated in the MIB, e.g., cases around the SS blockcenter, and/or cases of FMD with SS block.

FIG. 38 shows an example of RMSI CORESET location cases for the samesubcarrier spacing case.

The example shown in FIG. 38 provides some possible cases for RMSICORESET location when the subcarrier spacing is the same as the SSblock.

FIG. 39 shows an example of RMSI CORESET location cases for thedifferent subcarrier spacing case.

The example shown in FIG. 39 illustrates some possible cases for RMSICORESET location when the subcarrier spacing is twice of that of the SSblock. It is possible to use 3 bits to indicate the possible cases foreach subcarrier spacing case.

In FIGS. 38 and 39, the example is for the case that SS Block is alignedwith the actual RB grid. In case that the SS Block may not be alignedwith actual RB grid, the indication can be defined in a similar way bydefining the specific reference location for SS block and RMSI CORESET.To further reduce the signaling overhead, the subcarrier spacing,frequency location, BW, time domain information can be separatelyindicated or partially/fully encoded based on the signaling requirement.

RMSI Time Resource Indication in MIB

The RMSI CORESET time domain information can be defined by the startingsymbol in the slot, and the number of symbols for the CORESET. Thestarting symbol can be the 1^(st) OFDM symbol in the slot, or alignedwith the first symbol of the SS block(s) in a slot, or the startingsymbol can be the 1^(st) OFDM symbol after the SS block(s) in a slot.The number of symbols for CORESET can be 1, 2 or 3. The CORESET startingOFDM symbol and duration can be separately indicated, or jointlyindicated, or encoded jointly with other parameters, e.g., CORESETsubcarrier spacing and/or CORESET frequency resource information.

The periodicity of RMSI transmission can be fixed in the specification,e.g., 80 ms. The periodicity of RMSI transmission can be pre-defined perfrequency range, e.g., 80 ms for below-6 GHz and 160 ms for above-6 GHz.Or, the periodicity of RMSI transmission it can be configured based on apre-defined set of periodicity values. The periodicity values can be aninteger multiple of PBCH transmission periodicity. The configuration isindicated in MIB, e.g., log₂ M bits to indicate M periodicitypossibilities. Different set of periodicity values can be used indifferent frequency ranges, and hence the number of indications can bedifferent.

During a RMSI period, there can be one or multiple RMSI transmissions,which can be the repeated transmissions, or beam-swept transmissions.The number of RMSI transmissions can be fixed or pre-defined perfrequency range. Or, the number of RMSI transmission can be determinedby the periodicity, if there are multiple possible periodicities.Similarly, the number of RMSI transmission can be configured based on apre-defined set of transmission number values. Different set oftransmission number values can be used in different RMSI periodicitycases and can be different in different frequency ranges, and hence thenumber of indications can also be different. The configuration of thetransmission number can be indicated in MIB, e.g., log₂N bits toindicate N possibilities.

Given the RMSI periodicity of P radio frames and number of RMSItransmissions of R per period, the time information for RMSItransmission, e.g., frame index, subframe or slot index, and so on, canbe derived based on a pre-defined rule. The frame duration can bepre-defined, e.g., 10 ms. The subframe duration can be pre-defined,e.g., 1 ms. The slot duration can be defined by a pre-defined number ofOFDM symbols based on the numerology used by the SS block, e.g., 14symbols. If there is a configured numerology for RMSI transmission inMIB, the slot duration can be defined by a pre-defined number of OFDMsymbols based on the configured numerology. If the slot duration can beconfigurable, it can be indicated in the MIB.

During a RMSI period with P radio frames, the R times of RMSItransmissions can be located in N frames, and each frame includes r RMSItransmissions, where R=Nr, N≥1, r≥1. Given the RMSI period with P radioframes, N and r can be determined by a pre-defined rule. In somescenarios, one value can be pre-defined or implicitly derived based onthe RMSI period or number of RMSI transmissions and another value can bederived accordingly. For example, if a certain condition is satisfied,e.g., the number of RMSI transmission R is equal to or less than theRMSI period P, it can be assumed that there is one RMSI transmission inone frame, i.e., r=1, and hence the number of frames for RMSItransmission is

$N = {\frac{R}{r}.}$

During the RMSI period with P radio frames, there can be one RMSItransmission every d radio frames, where

$d = {\frac{P}{N}.}$

If P<R, there can be multiple RMSI transmissions in a radio frame. Forexample, there can be

$r = \frac{R}{p}$

RMSI transmissions every radio frame. Or, there can be pre-defined or aconfigured number of r RMSI transmissions in a radio frame, and hencethere are

$N = \frac{R}{r}$

radio frames for RMSI transmissions. Similarly, during the RMSI periodwith P radio frames, there can be one RMSI transmission every d radioframes, where

$d = {\frac{P}{N}.}$

The frame for RMSI transmission can be obtained by mod(SFN,d)=0. Or, theframe for RMSI transmission can be obtained in a cell-specific manner,e.g., by mod(SFN,d)=mod(N_(cell) ^(ID),d), which N_(cell) ^(ID) is thephysical cell ID derived based on PSS and SSS. The set of slots orsubframes in the frame for RMSI transmission can be pre-defined. The setof slots or subframes in the frame for RMSI transmission can beconfigurable by 1 bit indication that if the RMSI transmission framesare determined by a pre-defined rule or a cell-specific manner. Forexample, based on 1 bit configuration, the UE knows that the mapping ispre-defined or cell-specific.

The slot or subframe in the frame for RMSI transmission can bepre-defined based on a look-up table. For example, if there is one RMSItransmission in a radio frame, the pre-defined slot index is n₁. Ifthere are two RMSI transmissions in a radio frame, another slot withindex n₂ is additionally configured. Or, another two pre-defined slots(different from n₁) can be configured.

Transmissions in a radio frame Slot index in the radio flame r = 1 n₁ r= 2 n₁, n₂ r = 3 n₁, n₂, n₃ r = 4 n₁, n₂, n₃, n₄ . . . . . . r = r_(i)n₁, n₂, n₃, . . . , n_(r) _(i)

There can be a pre-defined pattern applied to multiple RMSItransmissions. For example, for single beam based RMSI transmission, toobtain diversity from channel coding, different redundancy version ofthe coded bits of RMSI massage can be used in the different RMSItransmissions. The orders of the used redundancy versions can bepre-defined for different number of RMSI transmissions. Or, theredundancy version of a certain RMSI transmission can be a function ofthe radio frame number and/or the subframe/slot index of thecorresponding RMSI transmission. The UE can combine the RMSItransmissions with different redundancy versions in a RMSI period fordecoding. If the RMSI transmissions in a RMSI period are based on beamsweeping, i.e., each transmission is applied with one or multipledistinct transmission (TX) beams, the pattern of applied beams can bethe same as the pattern applied in the SS blocks in the SS period. Onebit can be used to indicate if there is association of the pattern ofapplied beams in RMSI transmissions as the pattern used for SS blocks.If it is indicated that there is association, the pattern of the appliedbeams in the RMSI transmission can be determined by the beam patterns ofthe SS blocks. For example, if the number of RMSI transmissions in aRMSI period is the same as the number of SS blocks in a SS burst period,it can be assumed that the same set of beams is used for SS block andRMSI, and the order of the used beams is the same. If the number of RMSItransmissions is less than the number of SS blocks in a SS burst period,e.g., M times smaller, it can be assumed that the same set of beams isused for SS block and RMSI, but one beam for one RMSI transmission iscomposed of a composite beam of M beams used for M SS blocktransmissions. There is a sequential mapping order between the beamsused for SS block transmission and RMSI transmission.

The overall indication of RMSI transmission can be defined by a set ofindices; each corresponds to a set of parameters for RMSI transmission,e.g., a predefined periodicity, a pre-defined number of RMSItransmissions in the period, etc. An example is shown in the look-uptable below. Different configuration table with different parameters(e.g., periodicity and number of RMSI transmissions) can be used fordifferent frequency bands. The number of incitation bits can bedetermined by the number of configuration indices; e.g., log₂N bits formaximum of N configurations. Some parameters can be implicitly derived,e.g., the patterns of multiple RMSI transmissions based on a pre-definerule. After UE obtains the configuration index, the UE derives theconfiguration parameters of RMSI transmissions for receiving RMSI.

Number Config- Total number of RMSI uration of RMSI transmissionsTransmission Index Periodicity transmissions in a radio frame Pattern 0P₀ R₀ r₀ Pattern₀ 1 P₁ R₀ r₀ Pattern₁ 2 P₀ R₁ r₁ Pattern₀ 3 P₁ R₁ r₁Pattern₁ . . . . . . . . . . . .

FIG. 40 is a block diagram of a terminal according to an embodiment ofthe disclosure.

Referring to FIG. 40, a terminal includes a transceiver 4010, acontroller 4020 and a memory 4030. The transceiver 4010, the controller4020 and the memory 4030 are configured to perform the operations of theUE illustrated in FIGS. 1 to 39, or described above. Although thetransceiver 4010, the controller 4020 and the memory 4030 are shown asseparate entities, they may be realized as a single entity like a singlechip. The transceiver 4010, the controller 4020 and the memory 4030 maybe electrically connected to or coupled with each other.

The transceiver 4010 may transmit and receive signals to and from theother network entities, e.g. a base station.

The controller 4020 may control the terminal to perform a functionaccording to one of the embodiments described above. For example, thecontroller 4020 may be configured to control the transceiver 4010 toreceive a SS block including at least one synchronization signal (e.g.,PSS/SSS) and a broadcast channel (e.g., (NR-)PBCH) from the basestation, identify an offset between the SS block and a RB grid fromsystem information in the broadcast channel, and determine the RB gridbased on the offset. The controller 4020 may be configured to controlthe transceiver to receive the offset in a master information blockthrough the broadcast channel. The offset may be a 4-bit PRB gridoffset. The offset may be defined based on a lowest subcarrier in the SSblock. The controller 4020 may refer to a circuitry, anapplication-specific integrated circuit (ASIC), or at least oneprocessor.

In an embodiment, the operations of the terminal may be implementedusing the memory 4030 storing corresponding program codes. Specifically,the terminal may be equipped with the memory 4030 to store program codesimplementing desired operations. To perform the desired operation, thecontroller 4020 may read and execute the program codes stored in thememory 4030 by using a processor or a central processing unit (CPU).

FIG. 41 is a block diagram of a base station according to an embodimentof the disclosure.

Referring to FIG. 41, a base station includes a transceiver 4110, acontroller 4120 and a memory 4130. The transceiver 4110, the controller4120 and the memory 4130 are configured to perform the operations of thenetwork (e.g., gNB) illustrated in FIGS. 1 to 39, or described above.Although the transceiver 4110, the controller 4120 and the memory 4130are shown as separate entities, they may be realized as a single entitylike a single chip. The transceiver 4110, the controller 4120 and thememory 4130 may be electrically connected to or coupled with each other.

The transceiver 4110 may transmit and receive signals to and from theother network entities, e.g. a terminal.

The controller 4120 may control the base station to perform a functionaccording to one of the embodiments described above. For example, thecontroller 4120 may control to determine a RB grid and a location of aSS block including at least one synchronization signal (e.g., PSS/SSS)and a broadcast channel (e.g., (NR-)PBCH)), control the transceiver 4110to transmit the SS block based on the RB grid to the terminal, andcontrol the transceiver 4110 to transmit an offset between the SS blockand the RB grid in system information through the broadcast channel tothe terminal.

The controller 4120 may refer to a circuitry, an application-specificintegrated circuit (ASIC), or at least one processor.

In an embodiment, the operations of the base station may be implementedusing the memory 4130 storing corresponding program codes. Specifically,the base station may be equipped with the memory 4130 to store programcodes implementing desired operations. To perform the desired operation,the controller 4120 may read and execute the program codes stored in thememory 1530 by using a processor or a central processing unit (CPU).

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. As used herein,including in the claims, the term “and/or,” when used in a list of twoor more items, means that any one of the listed items can be employed byitself, or any combination of two or more of the listed items can beemployed. For example, if a composition is described as containingcomponents A, B, and/or C, the composition can contain A alone; B alone;C alone; A and B in combination; A and C in combination; B and C incombination; or A, B, and C in combination. Also, as used herein,including in the claims, “or” as used in a list of items prefaced by “atleast one of” indicates a disjunctive list such that, for example, alist of “at least one of A, B, or C” means A or B or C or AB or AC or BCor ABC (i.e., A and B and C).

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

1. A method performed by a terminal in a wireless communication system,the method comprising: receiving, from a base station, a synchronizationsignal block (SSB) including at least one synchronization signal and aphysical broadcast channel (PBCH); identifying a subcarrier offsetbetween the SSB and a resource block (RB) grid based on systeminformation on the PBCH; and identifying a location of the SSB based onthe subcarrier offset, wherein the subcarrier offset is defined by anumber of subcarriers from a lowest subcarrier in a lowest RBoverlapping with the SSB to a lowest subcarrier in the SSB, wherein avalue indicating the subcarrier offset is included in a masterinformation block on the PBCH, and wherein the subcarrier offset isindicated by a 4-bit value.
 2. The method of claim 1, whereininformation on the lowest RB is included in a system information block 1received from the base station.
 3. The method of claim 1, wherein an RBin the RB grid includes 12 consecutive subcarriers in a frequencydomain.
 4. The method of claim 1, wherein a subcarrier spacing of thelowest RB is assumed as 15 kHz.
 5. A method performed by a base stationin a wireless communication system, the method comprising: determining aresource block (RB) grid and a location of a synchronization signalblock (SSB) including at least one synchronization signal and a physicalbroadcast channel (PBCH); and transmitting, to a terminal, the SSB basedon the RB grid, wherein information on a subcarrier offset between theSSB and the RB grid is transmitted in system information on the PBCH,wherein the subcarrier offset is defined by a number of subcarriers froma lowest subcarrier in a lowest RB overlapping with the SSB to a lowestsubcarrier in the SSB, wherein a value indicating the subcarrier offsetis included in a master information block on the PBCH, and wherein thesubcarrier offset is indicated by a 4-bit value.
 6. The method of claim5, wherein information on the lowest RB is included in a systeminformation block 1 transmitted to the terminal.
 7. The method of claim5, wherein an RB in the RB grid includes 12 consecutive subcarriers in afrequency domain.
 8. The method of claim 5, wherein a subcarrier spacingof the lowest RB is assumed as 15 kHz.
 9. A terminal in a wirelesscommunication system, the terminal comprising: a transceiver configuredto transmit and receive signals; and a controller coupled with thetransceiver and configured to: receive, from a base station, asynchronization signal block (SSB) including at least onesynchronization signal and a physical broadcast channel (PBCH), identifya subcarrier offset between the SSB and a resource block (RB) grid basedon system information on the PBCH, and identify a location of the SSBbased on the subcarrier offset, wherein the subcarrier offset is definedby a number of subcarriers from a lowest subcarrier in a lowest RBoverlapping with the SSB to a lowest subcarrier in the SSB, wherein avalue indicating the subcarrier offset is included in a masterinformation block on the PBCH, and wherein the subcarrier offset isindicated by a 4-bit value.
 10. The terminal of claim 9, whereininformation on the lowest RB is included in a system information block 1received from the base station.
 11. The terminal of claim 9, wherein anRB in the RB grid includes 12 consecutive subcarriers in a frequencydomain.
 12. The terminal of claim 9, wherein a subcarrier spacing of thelowest RB is assumed as 15 kHz.
 13. A base station in a wirelesscommunication system, the base station comprising: a transceiverconfigured to transmit and receive signals; and a controller coupledwith the transceiver and configured to: determine a resource block (RB)grid and a location of a synchronization signal block (SSB) including atleast one synchronization signal and a physical broadcast channel(PBCH), and transmit, to a terminal, the SSB based on the RB grid,wherein information on a subcarrier offset between the SSB and the RBgrid is transmitted in system information on the PBCH, wherein thesubcarrier offset is defined by a number of subcarriers from a lowestsubcarrier in a lowest RB overlapping with the SSB to a lowestsubcarrier in the SSB, wherein a value indicating the subcarrier offsetis included in a master information block on the PBCH, and wherein thesubcarrier offset is indicated by a 4-bit value.
 14. The base station ofclaim 13, wherein information on the lowest RB is included in a systeminformation block 1 transmitted to the terminal.
 15. The base station ofclaim 13, wherein an RB in the RB grid includes 12 consecutivesubcarriers in a frequency domain.
 16. The base station of claim 13,wherein a subcarrier spacing of the lowest RB is assumed as 15 kHz.